Field of the Invention
The present invention relates to a sealing device according to a seal technique. The sealing device according to the present invention is particularly suitable for being used as a high-pressure seal.
Description of the Conventional Art
There has been conventionally known a sealing device 1 shown in FIG. 4A as a high-pressure seal. The sealing device 1 is adapted to seal so as to prevent a sealed fluid in a high-pressure side H from leaking to a low-pressure side L by being arranged between two members 51 and 52 facing to each other, and is combined by a seal ring 11 which is installed to an installation groove 53 provided in one member 51 of these two members 51 and 52 and comes into close contact with the other member 52, a first backup ring 21 which is arranged in an opposite side (the low-pressure side L) to the sealed fluid in the seal ring 11 and is comparatively hard, and a second backup ring 31 which is arranged between the seal ring 11 and the first backup ring 21 and is comparatively soft.
The installation groove 53 is formed into a groove having a rectangular cross section for being easily processed. The first backup ring 21 is provided with an end surface portion 21a which comes into contact with a side surface portion 53b in an opposite side to the sealed fluid in the installation groove 53 and is formed into an axially vertical plane, a peripheral surface portion 21b which comes into contact with the other member 52 and is formed into a cylindrical surface, and an inclined surface portion 21c which intersects the end surface portion 21a and the peripheral surface portion 21b, and is formed into a triangular cross section. The second backup ring 31 is provided with an end surface portion 31a which is brought into contact with the seal ring 11 and is formed into an axially vertical surface, a peripheral surface portion 31b which comes into contact with a bottom surface portion 53a of the installation groove 53 and is formed into a cylindrical surface, and an inclined surface portion 31c which is provided in correspondence to the inclined surface portion 21c of the first backup ring 21, and is formed into a triangular cross section in the same manner.
In the sealing device 1 having the structure mentioned above, since the first backup ring 21 is arranged in the opposite side (the low-pressure side L) to the sealed fluid in the seal ring 11, the seal ring 11 can be prevented from breaking by protruding to a gap 54 between two members 51 and 52. Further, since the second backup ring 31 is arranged between the seal ring 11 and the first backup ring 21, the seal ring 11 can be prevented from breaking by protruding to a gap (not shown) between the first backup ring 21 and the other member 52.
However, in the sealing device 1, since a corner portion 21d, where the end surface portion 21a and the inclined surface portion 21c in the first backup ring 21 intersect, is formed into a pointed shape, and a corner portion 31d, where the peripheral surface portion 31b and the inclined surface portion 31c in the second backup ring 31 intersect, is also formed into a pointed shape, the following problems are pointed out.
More specifically, when two members 51 and 52 are decentered each other as shown in FIG. 4B, the corner portion 21d having the pointed shape in the first backup ring 21 interferes with the bottom surface portion 53a of the installation groove 53 at a portion C on the drawing which is circumferentially a part, and is collapsed. Therefore, since the comparatively hard first backup ring 21 is collapsed as mentioned above, a breakage such as a crack may be generated in the first backup ring 21. Since the corner portion 21d is positioned in an inner corner portion where the bottom surface portion 53a and the side surface portion 53b intersect in the installation groove 53, the corner portion 21d has no way out even if it is exposed to a load. Therefore, the corner portion 21d tends to be collapsed and be broken (a first problem due to interference).
Further, when two members 51 and 52 are decentered each other as shown in FIG. 4B, the corner portion 31d having the pointed shape in the second backup ring 31 interferes with the side surface portion 53b of the installation groove 53 at a portion D on the drawing which is circumferentially a part, and is collapsed in the same manner. Further, since the second backup ring 31 is comparatively soft, the breakage such as the crack is not generated. However, since the collapsed corner portion 31d has no way out, the corner portion 31d is pressed to the first backup ring 21. As a result, a gap is generated in relation to the first backup ring 21 and the second backup ring 31 is inclined. Therefore, a gap (not shown) is generated between the second backup ring 31 and the bottom surface portion 53a of the installation groove 53, and the seal ring may protrude to the gap and break (a second problem due to interference).